Articular replacement



Oct. 4, 1955 5 s, HUDAcK 2,719,522

ARTICULAR REPLACEMENT Filed July 8, 1952 INVEN 575mm 5 Hum (34mm 6. m

H15 flTTOK V Y United States Patent ARTICULAR REPLACEMENT Stephen S.Hudack, Enumclaw, Wash., assignor, by mesne assignments, to the UnitedStates of America as represented by the Secretary of the NavyApplication July 8, 1952, Serial No. 297,742

Claims. (Cl. 128-92) This invention relates to improvements in ostealappliances, and more particularly pertains to improvements in articularreplacements for surgically excised bone.

Where it becomes necessary to excise surgically a part of a human boneand to replace the excised element with an osteal appliance, severaldesiderata must be considered. The structural strength of live bone mustbe provided in the resultant compound of live bone and replacementelement. The replacement element must be able to withstand the constantminute vibratory muscular strains that will be imposed. Such elementmust also be unaffected by the highly corrosive chemical and electrolytic action in the body.

Particularly where an articular replacement is involved, there must be adispersion of stress on the host tissue, as by decreasing the angle ofthe neck, expanding the surface area of the host tissue to avoid unduestress concentration and by elimination of screw-fixation techniques.Undisturbed vascular supply to the host tissue taking the compressionstrain must be maintained, since preservation of the bone element withimpaired blood supply leads to necrosis and collapse. In addition, infemoral replacements, there must be maintenance or restitution of formand function, with preservation and reattachment, insofar as possible,of the ilio-psoas groups, the rectus femoris, the glutei groups, thetensor fascia femoris and the small external rotator muscles.

The principal object of this invention is to provide an osteal applianceaffording a substantial equivalent and a substitute for surgicallyexcised bone.

Another object is to provide an articular replacement for surgicallyexcised bone.

Still another object is to provide an articular replacementsubstantially equivalent in structural strength, resistance tovibration, and chemically and electrolytically inert quality to humanbone, wherein stress dispersion, affording of optimum vascular supply tothe host tissue, and maintenance of restitution of form and function areachieved.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawing wherein:

Fig. 1 is an elevation of a portion of the ilium and a partially excisedfemur with fixation thereinbetween of an articular replacement, showinga preferred embodiment of the invention. (Relevant musculature isomitted for purposes of clarity.)

Fig. 2 is an enlarged side elevation of the articular replacement shownin Fig. 1;

Fig. 3 is a section taken on the line 33 of Fig. 2;

Pi g. 4 is a section taken on the line 44 of Fig. 2;

Fig. 5 is a section taken on the line 55 of Fig. 2; and

Fig. 6 is a section taken on the line 66 of Fig. 2.

Similar numerals refer to similar parts throughout the several views.

The articular replacement comprises a head 13 and 2,719,522 PatentedOct. 4, 1955 shank 14 adapted to be seated in a femur 18 the upperportion of which has been excised. The head 13 is preferably a curedmethyl methacrylate polymer having no undiffused monomers, dimers ortrimers, no plasticizer contaminant, and no bubbles, craze marks orother evidence of internal strain. Said head 13 comprises asubstantially spherical or bulbous femoral head portion 15 havingsubstantially the diameter of the excised femoral head to assure facilearticulation in the cotyloid cavity of the innominate bone 16. Said headportion 15 flares into a substantially cylindrical throat portion 17somewhat below the major dimension thereof, the axes of the head andthroat portions defining an angle substantially equal to thecorresponding angle of the excised portion of the femur.

A first fin or car 19 that extends radially from the throat portion atthe center of the lateral side thereof and flares into the head at allmeeting surfaces is provided with a plurality of holes 21 for theinsertion of selected muscles having their origin in the innominatebone. Additional fins or cars 23 and 25 extend radially from the throatportion, each at a radial angle of approximately 45 from the ear 19 toprovide a general symmetry, and each of said ears 23 and 25 flares intothe head at all meeting surfaces. A plurality of holes 27 in ear 23 anda plurality of holes 29 in ear 25 are provided for the insertion ofselected muscles having their origin in the innominate bone. The shank14 is preferably a hexamethylene diamine adipate polymer such as theDupont nylon formula 10,001 fabricated by the Polymer Corp. of Reading,Pa. It must be free of internal strain, quick-cooled to preventcrystallization that gives a predisposition to brittleness and radialfracture, and must be so fabricated as to be uncontaminated by otherplastics or by other nylon formulas which may contain irritativeimpurities. Said shank 14 comprises a threaded stud 31 that extendsabove the upper face 33 to mate with an internally threaded bore 35 inthe throat portion 17 and secure said shank in precise and coextensiveabutment with the lower face 37 of the said throat portion 17, agenerally frusto-conical intermediate portion 39 having smooth opposedflats 41 and a plurality of symmetrical grooves or flutes 43 extendinglongitudinally along the surface thereof, and an elongated tapered endportion 45 having a plurality of annular grooves or flutes 47. Saidintermediate portion 39 and end portion 45 are integral elementscharacterized by a smooth transition with their respective meeting endsas shown in Figs. 1, 2 and 3. A threaded bore 49 extends through theupper shoulder 51 of the intermediate portion 39 and further eX- tendsinto the throat portion 17 to receive a molybdenum stainless steel screw53, primarily to provide a reference marker to indicate post-operativelyany rotation of the articular replacement and secondarily to preventrelative rotation of the head 13 and shank 14.

The operative procedure recommended for articular replacement of theupper portion of the femur with the subject device comprises the stepsof exposure, excision, seating and closure. In exposure, the anteriorSmith-Petersen approach is preferred, since the lateral or posteriorapproaches do not seem to give enough access to the anterior and mesialacetabulum. Whenever possible, the rectus femoris and its attachment aresaved. Adequate detachment from both faces of the innominate bonecontributes to ease of dislocation, excision of the femur and revisionof the acetabulum. The capsule is then excised as completely as possibleto remove diseased and scar tissue and to allow for greater operativeflexibility. The amount of femur to be excised is estimated, allowingfor restitution of length where possible. (Unless there is tumor ordestruction of the greater trochanter it should be preserved. Thetransection of the femur should be above the lesser ice trochanter whenpossible. Accurate planographs or distortion-corrected X rays of thenormal side (if there is one) also aid in reconstructing toapproximately the desired nor ms) The-estimated segment is then excisedwith or without dislocation, depending upon limitation of movement,posterior scarring deformation and other factors. Where the outer shellof the greater trochanter is saved, the excision of the posteriorcapsule is then completed. Essentially, such excision dene'rvates thejoint and reduces postoperative pain and muscle spasm, making activemotion possible on the first postoperative day.

:In seating the subject device, the marrow canal is opened and itsipeculiarities felt out with an intrarnedullary pin. The canal isprepared for the seating and the length of the open gap tested to besure that the -fit for the head element is :not too snug and thatreduction is possible after the seating of the i-ntramedullary portion.The replacement element is seated with the patella straight up and theelement rotated externally about 25 degrees. It is then reduced andtested for motion, snugness and stability. (In seating, if fiexion andadduction contracture are present and long standing, the replacementelement should be adapted to allow optimum motion. When the anterioracetabulur lip is hypertrophied, it should be revised surgically toallow unimpaired flexion. When the acetabulum is shallow, as in chronicdislocation, it should be deepened to give a stable socket. When thejoint is fused or destroyed it should be i e-formed surgically toproportions as nearly normal as possible. The marrow canal of the upperfemur should be shaped to fit snugly the upper shank 39 to controltorque, and the fit should be good but not right. If fitting isdifficult, the upper femur can be split part way longitudinally toexpand the marrow canal. The split should of course, be lateral and notlong enough to weaken the femur structurally.)

Completing the surgery with the closure, the motor flanges are settledinto the trochanteric shell and sutured into place, .pulling the shellanteriorly to snug up the gluteal aponeurosis. Where possible, thereflected lateral portion of the rectus femoris is utilized, beingsutured to the anterior limit of the gluteal aponeurosis to stabilizeagainst lateral slipping. The deep covering of the tensor fascia femorisis sutured to the lateral limit of the rectus femoris and the layersclosed in. Where the foregoing reconstruction is deemed unstable,immobilization in plaster is effected. Otherwise, only a posterior shellwith a cross bar to prevent rotation is used.

Postoperative roen-tgenograms, the objective and subjectivepostoperative indicia of restoration of function and alleviation ofpain, and postmortem examinations have all supported the conclusion thatthe subject articular replacement accomplishes dispersion of stress onthe host tissue, permits undisturbed vascular supply to the host tissuetaking the compression strain and affords a striking maintenance orrestitution of form and function. Progressive new-bone formations overthe flats 41, and in the flutes 43 and grooves 47 is deemed a salientfactor in accomplishing these results.

The application of the subject invention to the problem ofarticular-replacement of the upper part of the humerus, as well as toother bone structure, is apparent. Obvious 1y, many modifications andvariations of the present invention are possible in the light of theabove teachings.

t is therefore to be understood that within the scope of the appendedclaims the invention may be practiced otherwise than as specificallydescribed.

I claim:

1. In an articular replacement for a host bone formation consisting ofarticulated bone structures, a head element of which one bone structureof the formation is host and a shank element of which another bonestructure of the formation is host, the head and shank elements beingsecured to each other rigidly, the shank element comprising a shoulderproximate to the head element and a conical portion extending away fromthe head element beyond the shoulder, the shank element comprising atapered portion remote from the head element and extending beyond theconical portion to the end of the shank element, the conical portioncomprising lands and grooves alternated circumferentially and extendinglengthwise of the shank element, the tapered portion comprising landsand grooves alternated lengthwise and extending transversely of theshank element, the head element being contoured to articulate with itshost bone structure of the formation, the shank element being adapted tobe projected into the medullary canal 'ofits host bone structure of theformation with its shoulder abutting against the excised end face of itshost bone structure and supporting the head element in articulatedrelationship with its host bone structure of the formation.

2. In an articular replacement as defined in claim 1, the head and shankelements being separate pieces and comprising respective attachingdevices companion to each other for securing the head and shank elementsto each other rigidly.

3. 'In an articular replacementas defined in claim 1, the head'elementcomprisingdevices located to be engaged by host musculaturehaving-origin in the host bone formation.

4. In an articular replacement asdefined in claim 2, the head elementconsisting of a cured methyl methacrylate polymer, and the shank elementconsisting of a hexamethylene diamine adipate polymer.

5. An articular replacement comprising a head element having a bulbous:portion adapted to be seated for articulation in the cavity of a hostbone formation and having a cylindrical portion bearing a plurality ofspaced radial fins, a plurality of holes in each of said fins adapted toreceive host musculature having origin in said host bone formation, ashank element having a threaded stud extending from an end thereofinserted into a threaded bore in the cylindrical portion of said headelement, said shank element having a longitudinally fluted substantiallyconica'l portion, opposed flats cut in said conical portion and anelongated tapered portion having a multiplicity of annular groovessubtended from said conical portion, said shank element being adapted tobe inserted into the medullary canal of a host bone at the excised endface thereof, and a pin threaded through a portion of said shank elementand into said head element.

References Cited in the file of this patent FOREIGN PATENTS 837,294Germany Apr. 21, 1952 989,341 France May 23, 1951 l,O47-,64O France July22, 1953 OTHER REFERENCES The Journal 'of Bone and Joint Surgery forJuly 1943, pp. 690-1.

1948 Catalog of Austental Laboratories, Inc., 224 E. 39 street, N. Y.'16, N. Y.; p. 25. Copy in Division 55.

The Journal of Bone and Joint Surgery for October 1951, advertising p.36.

The Journal of Bone and Joint Surgery for January 195 2, advertising p.4.

The Journal of the International College of Surgeons, for April 1951, p.499.

The Journal of Bone and Joint Surgery for October 1952 (paper read atmeeting in Chicago on January 20, 1952 pp. 989-90.

Copies of the publications in Scientific Library.

